What are the file name limitations in an FTP path?

Solution 1:

The FTP protocol specification does not impose any rules on a file path.

All it says (RFC 959, section 2.2) is:

Pathname is defined to be the character string which must be input to a file system by a user in order to identify a file. Pathname normally contains device and/or directory names, and file name specification. FTP does not yet specify a standard pathname convention. Each user must follow the file naming conventions of the file systems involved in the transfer.

The original specification allowed 7-bit characters only, but this restriction was dropped in later RFC 2640 (section 3), which requires UTF-8 encoding.

So any character or length rules are system- and/or implementation-specific.